Initially he spent £20 in a two-week period. After that we made him realise it cost 30 to 40p to call his friends and since then he's been quite prudent and the £10 has lasted around three months.

Both my wife and myself are aware of this report.

I think something came out about a year or two ago, so we've actually told him not to use the phone for calling - only use it mainly for texting - and he's also got games on his phone as well, so he could use it for that.

But we wouldn't let him use it for half an hour or anything like - definitely not.

If there was a definite risk we would stop him using it and make him use the home landline phone.